Recently, application of rice flour to fermented bakery products and noodles has been highlighted because rice is highly recognized as a healthy food. There are many suggestions for the process for producing unpolished- or polished-rice flour, which is favorable for producing bakery products and noodles as an substitute of wheat flour, using unpolished- or polished-rice as a material.
Unpolished rice flour is generally produced by the steps of roasting unpolished rice grains without polishing, and milling the resultant into flour. For example, a process for producing unpolished rice flour, comprising the steps of allowing to expand unpolished rice grains by heating and pressurizing, and drying and milling the resultant, was proposed as disclosed in Japanese Patent Kokai No. 22155/88. Also, as disclosed in Japanese Patent Kokai No. 45130/2002, a process for producing unpolished rice flour, comprising the steps of steaming unpolished rice grains, and drying and milling the resultant, has been proposed.
While, polished rice flour is generally produced by the steps of polishing unpolished rice by applying to a polisher for shaving bran, soaking the polished rice in water, and drying and milling the resultant by using various milling methods such as roll-type milling, impact-type milling, stamp-milling, and grinding with water. “JOSHINKO”, a kind of polished rice flour produced by roll-type milling, and “JOYOKO”, a kind of polished rice flour produced by stamp-milling are well known. Recently, there have been proposed several processes for producing polished rice flour, for example, a process comprising the steps of soaking rice grains in a solution comprising pectinase, dehydrating the resulting rice grains, milling the dehydrated rice grains to a fine rice flour, drying the flour to give a moisture content of about 15% (w/w) (hereinafter, “% (w/w)” is simply abbreviated as “%” in this specification), and baking the resulting flour at about 150° C. as disclosed in Japanese Patent Kokai No. 287,652/92; a process comprising the steps of soaking a material rice grains in a solution comprising enzymes such as hemicellulase, pectinase, and pectin esterase, drying the resulting rice grains, and milling the dried rice grains as disclosed in Japanese Patent Kokai No. 68,468/93; and a process comprising the steps of soaking rice grains in a solution comprising salts of organic acids and those with pectinase, dehydrating and drying the soaked rice rice grains, and milling the dried rice grains as disclosed in Japanese Patent Kokai No. 175,636/2000.
As described above, the processes for producing rice flour (throughout the specification, both unpolished- and polished-rice flours may be simply called as “rice flour”) are different depending on which unpolished-rice or polished-rice is used as a material, because the properties of those rice grain are different. Therefore, in the case of producing both unpolished- and polished-rice flours, there are disadvantages of requiring specific hardwares and processes, which are suitable therefor, and high costs for producing them. While, a method for producing rice flour from both unpolished- and polished-rice using a single process as above has been also proposed. For example, a process for producing rice flour, comprising the steps of soaking raw rice grains including unpolished rice into water which contains an amylase; freezing the soaked rice; and drying and milling the resultant, was disclosed in Japanese Patent No. 3,075,556. However, the process has disadvantages of requiring a process of freezing rice and a relatively high cost for the production.
The present invention was accomplished to solve the above various disadvantages of conventional processes for producing rice flour. The first object of the present invention is to provide a process for producing rice flour, which enables to prepare unpolished- and polished-rice into rice flours in an single method on an industrial scale and inexpensively. The second object of the present invention is to provide rice flour produced by the process and uses thereof for producing bakery products and noodles.